1. Field of the Invention
The present invention relates to a semiconductor apparatus having plural parts packaged in one module, particularly a semiconductor apparatus having capacitors connected outside semiconductor elements for improving high frequency characteristics. It also relates to a production process thereof.
In this specification, in the case where plural semiconductor devices are arranged as a module to constitute a semiconductor apparatus, the respective semiconductor devices are called semiconductor elements. LSIs such as CPU are also called semiconductor elements.
2. Description of the Related Art
In recent years, the system-in-packages, in which existing chips are combined and connected at high densities to realize desired functions, are increasingly used. Compared with the case of integrating all functions on one chip, the development period can be shortened, and the cost performance can be improved.
Furthermore, semiconductor elements such as digital LSIs are advancing to be higher in speed and lower in power consumption. Because of the lower power consumption, the supply voltage declines. For example when the load impedance changes suddenly, the supply voltage is likely to vary. If the supply voltage varies, the semiconductor element is functionally disordered. So, the role of the decoupling capacitors for inhibiting the variation of supply voltage is important.
Since semiconductor elements are growing to be higher in speed, the influence of high frequency ripple is increasing. It is desired that the decoupling capacitors can also efficiently absorb the high frequency ripple component.
Because of the above, it is desired to lower the equivalent series resistance (ESR) and equivalent series inductance (ESL) of the capacitors. For this purpose, it is desired to minimize the wiring lengths between the semiconductor chips and the capacitors.
In the system-in-package, for connecting decoupling capacitors or the like to semiconductor chips or circuit substrate, there are known such techniques as (1) resin buildup technique, (2) thick ceramic film technique and (3) thin film multilayer technique.
(1) In the resin buildup technique, with a printed board used as the substrate, an insulation layer, passive element layer and wiring layer are built up on it, and capacitors are formed immediately below semiconductor chips and are connected by means of through wires. If an organic insulation layer is used as the insulation layer, the cost can be reduced, and the process can be carried out at low temperature. Furthermore, the thermal stress caused by heat cycles after mounting can be decreased, if the difference between the passive elements and the insulation layer in thermal expansion coefficient is kept small.
If capacitors are disposed immediately below semiconductor chips, ESL can be lowered, but the pitch of through wires in the capacitor support is as relatively large as 50 to 200 μm. The obtained capacitances of the capacitors are hundreds of picofarads per square centimeter, and this is insufficient as decoupling capacitors at high frequency.
(2) In the thick ceramic film technique, a low loss ceramic material is used as a substrate and an insulation layer, and a dielectric layer and a resistance layer are burned integrally. Capacitors can be formed immediately below semiconductor chips, and can be connected by means of through wires. The structure is excellent in parts-accommodating capability and low in dielectric loss (tanδ). So, the transmission loss at high frequency is small.
The obtained capacitance is tens of nanofarads per square centimeter, and the function as decoupling capacitors at high frequency is insufficient. Since the ceramics shrink in volume when burned, the dimensional dispersion becomes large. So, the through wire pitch in the capacitor support is as large as about 100 to 200 μm.
(3) In the thin film multilayer technique, a low dielectric constant resin is used as an insulation layer, and silicon or glass is used as a substrate. Resistances and capacitors can be formed in the layer, and the capacitors can be connected immediately below semiconductor chips by means of through wires. If the process is carried out at high temperature, capacitors having large capacitance of hundreds of nanofarads per square centimeter can be obtained.
If a semiconductor process is used, the through wire pitch in the support can be made as small as about 20 to 50 μm. The thermal stress caused by heat cycles after mounting can be decreased if the difference between passive elements and the insulation layer in thermal expansion coefficient is kept small.
Semiconductor elements are growing further higher in operation speed, lower in power consumption and larger in area. The transistors and wires in each semiconductor element become finer and finer. The number of terminals of a semiconductor element is also increasing, and the pitch between terminals is diminishing. There is a limit in narrowing the through wire pitch in the support of decoupling capacitors in accompany with the pitch of terminals of a semiconductor element.
If capacitors are mounted near, not immediately below, semiconductor elements, capacitors with large capacitance can be realized at low cost. However, since the wires must be routed longer, the high frequency characteristics become worse. It becomes difficult to install decoupling capacitors suitable for semiconductor elements acting at high speed at a frequency of more than GHz.
As described above, the system-in-package encounters a restriction in suitably connecting semiconductor elements, electronic parts such as capacitors, and a circuit substrate.